Antimicrobials

The immune system protects the body from infection and creates a collection of reactions and responses in order to defend the body. Cancer can affect the immune system by spreading into the bone marrow which is more common in Leukaemia and Lymphoma patients but can happen in other cancers too. Chemotherapy, radiotherapy and steroids can additionally affect the immune system.  

Following your consultation at the Care Oncology Clinic, you may be prescribed courses of Doxycycline and/or Mebendazole which are both useful prophylactic (preventative) medications. Both can be used even when there is no sign of active  infection, in order to support and help a weakened immune system. 

Version 1.0 (Created December 2013) 

Doxycycline is a broad spectrum antibiotic part of a group of drugs called Tetracyclines. Doxycycline works by interfering with the ability of bacteria to produce proteins that are critical to them. Without these proteins the bacteria cannot grow and the Doxycycline therefore stops the spread of the infection and the remaining bacteria eventually die. However, scientific data suggests that this group of medications can additionally benefit patients suffering from cancer by interfering with the cell growth cycle by entering the cancer cells, disturbing their energy source and consequently slowing the development of cancer.  

Mebendazole is an antiparastic medication used to treat certain types of worm infestations of the gut and is part of a group of drugs called Anthelmintics. Mebendazole works by preventing the worms from being able to absorb the sugars that are essential for their survival and scientific data suggests it could do the same to your cancer.  

In cancer, studies have also shown that mebendazole inhibits tubulin formation inducing mitotic arrest which in turn induces apoptosis (cell death) in cancer cells.  

In addition, mebendazole inhibits pyruvate kinase, a key enzyme in the glycolytic pathway which is dominant in cancer cells 

THE IMMUNE SYSTEM 

The immune system is the body's defence against bacteria, viruses and other foreign organisms or harmful chemicals. It is very complex and has to work properly to protect us from harmful bacteria and other organisms in the environment, which may infect our bodies. Due to the fact that patients with cancer have a weakened immune system, they are more susceptible to becoming unwell. By giving broad spectrum anti-bacterial drugs as a preventative measure, they will help you fight off any infections you come into contact with.  

WHEN ARE THESE MEDICINES GIVEN? 

Your doctors will tailor a dose and regime of one or both the drugs discussed, specific to your own needs and condition which may change after each consultation.  

SIDE EFFECTS  

This information should be read with the information leaflet contained inside the packaging of your medicines.  

Everyone reacts differently when taking medications. Whilst some people may experience side effects, others may not suffer any side effects at all. If you do experience any side-effects, please consult the Care Oncology Clinic for advice.  

Below is a list of the most common side effects. Please be aware that although side effects can be difficult to manage, it is important to appreciate the very real benefits your medication can provide. Your GP may be able to prescribe you medications that will counteract troublesome side effects. 

DOXYCYCLINE: 

Yeast infections 

Throat irritation 

Loss of appetite 

Feeling sick 

Being sick 

Skin may become more sensitive to sunlight 

Indigestion 

Abdominal pain 

Diarrhoea 

MEBENDAZOLE: 

Stomach pain 

Diarrhoea 

Flatulence (wind) 

Stomach discomfort 

The package insert inside the packaging of your medications will contain a more comprehensive list of rarer side effects.  

THINGS TO REMEMBER 

 Using antibiotics in this way does not prevent all infections, so it’s still important to use the same precautions as when you are not taking prophylactic antibiotics. 

 If at any time, your GP or oncologist prescribes a course of treatment antibiotics and this coincides with a period during which you are taking doxycycline, please contact Care Oncology Clinic for further advice. If you are taking mebendazole during this period, it is ok to combine the treatment antibiotic and mebendazole.  

 Cimetidine may decrease the breakdown of mebendazole by the liver and so increase the amount of mebendazole in the blood. 

 The manufacturer recommends that mebendazole should not be used in combination with the antibiotic metronidazole. 

 Do not take indigestion remedies, or supplements containing iron, magnesium, or zinc at the same time as you take doxycycline. This is because doxycycline combines with these things and makes it less effective. If you need to take these preparations, make sure you leave at least two hours before or after taking doxycycline before you have them. 

 Due to the fact doxycycline can make skin more sensitive to sunlight, when taking it, try to stay out of direct sunlight, wear protective clothing and apply sunblock as appropriate.  

REFERENCES 

Doxycycline 

Inhibition of DNA-PK, ability to target cancer stem cells, radio-sensitisation of cancer cells. http://www.ncbi.nlm.nih.gov/pubmed/26087309 http://www.ncbi.nlm.nih.gov/pubmed/25625193

Inhibition of matrix metalloproteinases (MMPs); treatment of metastasis. http://www.ncbi.nlm.nih.gov/pubmed/14597870

Mebendazole 

Inhibition of tubulin formation inducing mitotic arrest which in turn induces apoptosis in cancer cells http://www.ncbi.nlm.nih.gov/pubmed/12479701 http://www.ncbi.nlm.nih.gov/pubmed/2 1764822  

Inhibition of pyruvate kinase, a key enzyme in the glycolytic pathway of glycolysis which is dominant in cancer cells  http://www.ncbi.nlm.nih.gov/pubmed/8010090.   

Macmillan Cancer Support – Advice on avoiding infection 

http://www.macmillan.org.uk/information-and-support/coping/side-effects-andsymptoms/other-side-effects/avoiding-infection.html